Voltage Regulation and Reactive Power Control Units for the Grid Integration of Renewable Power Generation in Distribution Networks

Summary

Due to increasing power infeed of highly volatile energy sources connected to distribution grids, innovative grid regulation units are needed to ensure grid stability and fulfil grid codes. The ability of photovoltaic and wind power plants to regulate the reactive power flow and therefore to prevent voltage swells generally depends on the supplying grid voltage. Especially in medium voltage grid areas with long cable extensions, low short-circuit power and fluctuating power flows, grid codes at the connecting point widely cannot be met. In this regard a simple and applicable solution can be found in Voltage Regulating Distribution Transformers (VRDT) using on-load-tap-changer (OLTC). Initially designed to be used as a control device to provide flexibility and adjustments between medium and low voltage grids, they can also be applied as regulated transformers in e.g. wind turbines. Furthermore, OLTCs constitutes the innovative switching element in variable shunt reactors (VSR). This application can be used for controllable reactive power compensation in case of long cables with high capacitive loading currents. Summarized in this paper, two new technologies for fulfilling auxiliary services in distribution networks are represented. Here, the focus is placed on grid integration concepts and operating experiences, complemented by references to a possible certification procedure for controlled components, which can provide a reliable grid integration of renewable power plants in distribution grids.

Additional informations

Authors

Jenau Frank, Takamoto Kiyoshi, Nishikawa Seiichi